Within biotechnology, the chromatographic methods suggested up to date are based on different modes of interaction with a target. Thus, for example, in ion-exchange chromatography, the functional groups are permanently bonded ionic groups with their exchangeable counter ions of opposite charge.
Chromatographic media normally used for ion exchange chromatography of biomolecules are substituted with a suitable charged ligands homogeneous distributed in the beads. To accomplish the salt-gradient and/or the pH-gradient for elution of adsorbed biomolecules a gradient is obtained by using to two pumps with different eluents. Initially the non-displacing mobile phase pump conveys most (if not all) and the displacing mobile phase pump very little (or even nothing) of the flow through a chromatography media. The flow-rate of each pump is then modified either continuously or intermittently to obtain gradients suitable for elution of adsorbed compounds.
A simpler method of running ion exchange chromatography than using the conventional two pump setups for generation of salt-gradient and/or the pH-gradient for elution of adsorbed sample molecules would be desirable in many instances.